Pick and Pack 3PL fees

I have a really great FBA prep center that only charges 30 cents to receive and FNSKU sticker. However, their pick and pack fee for FBM is $2.25 all in.

Is $2.25 a decent rate for 3PL FBM or can I do a lot better? Just looking at the shipmonk site it looks like they are below $2 if you do volume but I have no idea what other hidden charges there are.